A major requirement for a versatile and stable position probe assembly exists in the nuclear reactor field where knowledge of the precise position of control rods affecting the position of nuclear fuel rods is essential. The critical requirements for control rod position indicators for use in nuclear reactor facilities extend to both the mechanical design as well as to the electrical readout.
Typically, the probe assemblies required for monitoring control rod position can vary in length from two to twelve feet, thus requiring substantial overhead clearance for installation. In many facility designs the overhead clearance required to accommodate conventional rigid control rod position probe assembly does not exist. Efforts to date to design a suitable sectionalized or flexible position probe assembly capable of being installed and removed from a reactor facility having a clearance less than the overall length of the probe have not proven to be totally reliable over an extended period of time.
In addition to the mechanical deficiencies of prior art position probe assemblies, the analog manifestation of the position indication developed by these probe assemblies have not proven satisfactory due to the adverse effects of temperature changes, line voltage and frequency variations, noise pick-up, and, interference from ambient magnetic fields.
There is disclosed herein with reference to the accompanying drawings a unique probe design capable of flexing in two planes for ease of installation in facilities with limited overhead clearance, and developing a phase encoded electrical indication of the position of a magnetically permeable material, and signal processing circuitry for converting said phase encoded signal to a direct digital indication of the position of the magnetically permeable material.